Hi,
I've encountered a bug, so I decided to report it - a bug regarding map and minimap sprites. I don't know, how to explain it, so I just show you:

Capture.PNG (128.16 KiB) Viewed 124 times

This happens to me quite often on my machine since I started playing it on this machine (it's about 6 weeks = 6 new Factorio versions without a fix). Doesn't matter on zoom level, In game (standard, no-map view) there are no problems. I think it more related to graphics settings and machine specs rather than a map save. Used latest Factorio version
Graphics settings (in Czech):

I was exploring the map at the time, driving around to areas far from my normal base, in a car (or tank, can't remember), and on several occasions had a situation where the map/minimap would corrupt, exactly as the OP describes - although my corruptions looked a bit different.

Here's two screenshots I took at the time, when I posted about it on Reddit.

Screenshots

Then it stopped happening, and never happened again, so I didn't think any more about it. I've never seen it in 0.17.

At the time I was playing on 0.16.51, in macOS 10.14.1, on AMD 7970Ghz (R9 280X) 3GB GPU. Not sure as to graphical settings, but likely lowered from default.

I would suggest to update the graphics driver, but the one you have is already the latest one nVidia released for your GPU and you already play on the lowest graphics settings, so I don't have any software-side solution for this problem. You can try to disable "Use flip presentation model" and see if it makes any difference, but that's just a shot in the dark.